Integrating a ponderomotive guiding center algorithm into a quasi-static particle-in-cell code based on azimuthal mode decomposition
Integrating a ponderomotive guiding center algorithm into a quasi-static particle-in-cell code based on azimuthal mode decomposition
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DOI：
10.1016/j.jcp.2022.111599
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Fei Li;W. An;F. Tsung;V. Decyk;W. Mori
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文献类型：
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作者：
Fei Li;W. An;F. Tsung;V. Decyk;W. Mori
基于等离子体加速（PBA）的高保真建模需要使用三维的、完全非线性的、基于粒子单元（PIC）方法的动力学描述。在PBA中，强粒子束或激光（驱动器）通过稀薄等离子体传播，从而激发等离子体波尾流。基于准静态近似（QSA）的三维粒子模拟算法已成功地应用于相对论带电粒子束与等离子体相互作用的数值模拟。在QSA PIC算法中，基于来自驱动器的力和来自麦克斯韦方程的QSA形式的自洽力来计算对带电粒子束或激光驱动器的等离子体响应。然后，这些场用于使带电粒子束或激光向前推进大的时间步长。由于时间步长不受约束标准3D全电磁PIC码的常规Courant-Friedrichs-Lewy（CFL）条件的限制，因此3D QSA PIC码可以在性能上实现数量级的加速。最近，一种新的混合QSA PIC算法，结合另一种加速技术称为方位傅立叶分解已被提出和实施。该混合算法将电磁场、电荷和电流密度分解为方位谐波，并且仅需要更新傅立叶系数，这可以将3D代码的算法复杂度降低到2D代码的算法复杂度。在全三维电磁PIC算法中模拟激光-等离子体相互作用是非常昂贵的计算，由于要解决的物理尺度的巨大差异。在QSA中，激光器使用有质动力导引中心（PGC）方法建模。我们描述了如何实现一个PGC算法兼容的QSA PIC算法的基础上的方位角模式扩展。该算法允许时间步长大于细胞大小的数量级，它可以异步并行化。还描述了如何将其实现到利用方位角模式扩展QPAD的QSA PIC代码中的细节。基准和一个完全三维显式PIC代码（OSIRIS）之间的比较，以及几个例子有关的激光韦克菲尔德加速，提出。
High fidelity modeling of plasma based acceleration (PBA) requires the use of three dimensional, fully nonlinear, and kinetic descriptions based on the particle-in-cell (PIC) method. In PBA an intense particle beam or laser (driver) propagates through a tenuous plasma whereby it excites a plasma wave wake. Three-dimensional PIC algorithms based on the quasi-static approximation (QSA) have been successfully applied to efficiently model the interaction between relativistic charged particle beams and plasma. In a QSA PIC algorithm, the plasma response to a charged particle beam or laser driver is calculated based on forces from the driver and self-consistent forces from the QSA form of Maxwell's equations. These fields are then used to advance the charged particle beam or laser forward by a large time step. Since the time step is not limited by the regular Courant-Friedrichs-Lewy (CFL) condition that constrains a standard 3D fully electromagnetic PIC code, a 3D QSA PIC code can achieve orders of magnitude speedup in performance. Recently, a new hybrid QSA PIC algorithm that combines another speedup technique known as an azimuthal Fourier decomposition has been proposed and implemented. This hybrid algorithm decomposes the electromagnetic fields, charge and current density into azimuthal harmonics and only the Fourier coefficients need to be updated, which can reduce the algorithmic complexity of a 3D code to that of a 2D code. Modeling the laser-plasma interaction in a full 3D electromagnetic PIC algorithm is very computationally expensive due the enormous disparity of physical scales to be resolved. In the QSA the laser is modeled using the ponderomotive guiding center (PGC) approach. We describe how to implement a PGC algorithm compatible for the QSA PIC algorithms based on the azimuthal mode expansion. This algorithm permits time steps orders of magnitude larger than the cell size and it can be asynchronously parallelized. Details on how this is implemented into the QSA PIC code that utilizes an azimuthal mode expansion, QPAD, are also described. Benchmarks and comparisons between a fully 3D explicit PIC code (OSIRIS), as well as a few examples related to laser wakefield acceleration, are presented.